Dermatopathology Diagnosis

The best diagnosis is:

a. chondroma

H&E, original magnification 40. b. (chondroid syringoma) c. nerve sheath (neurothekeoma) CUTISd. nodular e. solitary adult myofibroma Do Not Copy

H&E, original magnification 100.

PLEASE TURN TO PAGE 235 FOR DERMATOPATHOLOGY DIAGNOSIS DISCUSSION

L. David Hall, MD; Tammie Ferringer, MD

Dr. Hall was from and Dr. Ferringer is from the Department of Dermatology, Geisinger Medical Center, Danville, Pennsylvania. Dr. Ferringer also is from the Department of Laboratory Medicine. Dr. Hall currently is from Ackerman Academy of Dermatopathology, New York, New York. The authors report no conflict of interest. Correspondence: L. David Hall, MD, Ackerman Academy of Dermatopathology, 145 E 32nd St, Floor 10, New York, NY 10016 ([email protected]).

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Solitary Adult Myofibroma

yofibromatosis can be classified based on its syringoma) may simulate myofibroma from low-power clinical presentation as either solitary infan- magnification, but it can be distinguished by the pres- Mtile myofibroma, congenital multiple myofi- ence of tubuloalveolar and ductal structures within the bromatosis without visceral involvement, congenital chondroid stroma (Figure 3). Nerve sheath myxoma generalized myofibromatosis with visceral involve- (neurothekeoma) displays myxoid lobules containing ment, or solitary adult myofibroma. Solitary adult spindle-shaped, stellate, or epithelioid cells (Figure 4), myofibroma is a benign proliferation of myofibroblasts and the lobules are separated by fibrous septa as opposed that most commonly presents as a firm superficial nod- to the hemangiopericytomalike vessels of myofibroma. ule on the skin or oral mucosa of young to middle-aged Nodular fasciitis should be included in the differential adults.1 In contrast, congenital generalized myofibro- diagnosis of myofibroma, as both are unencapsulated matosis shows a female predominance and typically nodules with variable amounts of myxoid stroma presents at or near birth as multicentric tumors with associated bone, oral, and potentially fatal visceral involvement.2 Histologically, solitary adult myofibroma and the infantile myofibromatoses are nearly identical. A well-circumscribed, often multi- lobular nodule is seen in the dermis or subcutaneous tissue with a characteristic biphasic pattern consisting of bland plump myofibroblasts and smaller, spindle- shaped mesenchymal cells (Figure 1). The spindle- shaped cells tend to be arranged around branching blood vessels that resemble hemangiopericytoma, also known as staghorn vessels, whichCUTIS may be seen in the center or periphery of the tumor (Figure 2).3 Unlike the infantile myofibromatoses, the adult variant tends to undergo hyalinization, resulting in a pseudochon- droid appearance.3,4 The histologic differential diagnosis may include Figure 2. Biphasic tumor of plump myofibroblasts within other multilobular dermal or subcutaneous tumors a pseudochondroid stroma and small mesenchymal withDo a mucinous or pseudochondroid Not stroma. The cells aroundCopy peripheral vessels resembling hemangio- architecture and stroma of mixed tumor (chondroid pericytoma (H&E, original magnification 100).

Figure 1. Subcutaneous tumor composed of nodular Figure 3. Small nonbranching ducts resembling eccrine aggregates of spindle-shaped cells with central pseudo- syringoma embedded within a myxoid and chondroid chondroid stroma and irregular vascular spaces periph- stroma of mixed tumor (H&E, original magnifica- erally (H&E, original magnification 40). tion 100).

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Figure 4. Multilobular dermal tumor comprised of deli- Figure 6. Subcutaneous tumor of mature cartilage with cate spindle-shaped and stellate cells within a loose chondrocytes occupying lacunae characteristic of chon- myxoid stroma characteristic of nerve sheath myxoma droma (H&E, original magnification 200). (H&E, original magnification 100). and thin-walled blood vessels. In contrast to myo- , nodular fasciitis is composed of plump, spindle-shaped cells arranged in a haphazard array (tissue culture appearance) with extravasated red blood cells and scattered lymphocytes (Figure 5). Chondroma is an encapsulated tumor of mature car- tilage and can be distinguished from myofibroma by CUTISthe presence of chondrocytes occupying individual lacunae (Figure 6).

REFERENCES 1. Daimaru Y, Hashimoto H, Enjoji M. Myofibromatosis in adults (adult counterpart of infantile myofibromatosis). Am J Surg Pathol. 1989;13:859-865. Do Not 2. ChungCopy EB, Enzinger FM. Infantile myofibromatosis. Cancer. 1981;48:1807-1818. Figure 5. Haphazardly arranged, plump, spindle- shaped cells within a myxoid stroma, giving a tissue 3. Elston D, Ferringer T, Ko C, et al. Dermatopathology: culture appearance characteristic of nodular fasciitis. Requisites in Dermatology. London, England: Elsevier; 2009. Extravasated red blood cells and sparse lymphocytes 4. Calonje JE, Brenn T, Lazar AJ, et al. McKee’s Pathology of also were noted (H&E, original magnification 200). the Skin. 4th ed. London, England: Elsevier; 2012.

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